Project planning in an interactive Gantt-Diagram
Resource planning view with allocations
Calendar view for tasks and resources
Calculation of project cost
Extremely small application, but with full blown feature set
64-bit native on 64-bit machines. Also runs on 32-bit systems.
Might this tiny little and well thought app replace MS-Project*) for you?
Multi-user / multi-project management with MS-SQL-Server

System Requirements:

All current versions of Windows
DotNet Framework 2.0 or above (already installed on the current versions of Windows)
Optional MS-SQL Server version 2005+, the free Express-Version is enough